• The Transactions of the Korean Institute of Electrical Engineers P
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• v.51 no.3
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• pp.120-125
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• 2002

The switching-mode power converter has been widely used because of its features of high efficiency and small weight and size. These features are brought by the ON-OFF operation of semiconductor switching devices. However, this switching operation causes the surge and EMI(Electromagnetic Interference) which deteriorate the reliability of the converter themselves and entire electronic systems. This problem on the surge and noise is one of the most serious difficulties in AC-to-DC converter. In the switching-mode power converter, the output voltage is generally controlled by varying the duty ratio of main switch. When a converter operates in steady state, duty ratio of the converter is kept constant. So the power of switching noise is concentrated in specific frequencies. Generally, to reduce the EMI and improve the immunity of converter system, the switching frequency of converter needs to be properly modulated during a rectified line period instead of being kept constant. Random Pulse Width Modulation (RPWM) is performed by adding a random perturbation to switching instant while output-voltage regulation of converter is performed. RPWM method for reducing conducted EMI in single switch three phase discontinuous conduction mode boost converter is presented. The more white noise is injected, the more conducted EMI is reduced. But output-voltage is not sufficiently regulated. This is the reason why carrier frequency selection topology is proposed. In the case of carrier frequency selection, output-voltage of steady state and transient state is fully regulated. A RPWM control method was proposed in order to smooth the switching noise spectrum and reduce it's level. Experimental results are verified by converter operating at 300V/1kW with 5%~30% white noise input. Spectrum analysis is performed on the Phase current and the CM noise voltage. The former is measured with Current Probe and the latter is achieved with LISN, which are connected to the spectrum analyzer respectively.

• Journal of IKEEE
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• v.15 no.4
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• pp.330-338
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• 2011

In this paper, a current-mode buck-boost converter using Multiple switching devices is presented. The efficiency of the proposed converter is higher than that of conventional buck-boost converter. In order to improve the power efficiency at the high current level, the proposed converter is controlled with PWM(pulse width modulation) method. The converter has maximum output current 300mA, input voltage 3.3V, output voltage from 700mV to 12V, 1.5MHz oscillation frequency, and maximum efficiency 90%. Moreover, this paper proposes watchdog circuits in order to ensure the reliability and to improve the performance of dc-dc converters. An electrostatic discharge(ESD) protection circuit for deep submicron CMOS technology is presented. The proposed circuit has low triggering voltage using gate-substrate biasing techniques. Simulated result shows that the proposed ESD protection circuit has lower triggering voltage(4.1V) than that of conventional ggNMOS(8.2V).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.8
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• pp.958-966
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• 2012

This paper presents a compact bluetooth/WiFi dual-mode dual-band RF front-end module(FEM) is realized by low temperature co-fired ceramic(LTCC) technology. The proposed RF front-end module consists of a diplexer, baluns in the LTCC substrate, and an SPDT switch, an SP3T switch on the LTCC substrate. In order to reduce the module size and increase integration level, the proposed diplexer and balun are designed using LC lumped elements. The parasitic elements caused by coupling effect between metal pattern layers and ground plane layer are considered during the design. The fabricated dual-mode RF front-end module has 13 pattern layers including three inner ground layers and it occupies less than $3.0mm{\times}3.7mm{\times}0.66mm$.

• Journal of Power Electronics
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• v.19 no.2
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• pp.403-412
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• 2019

Aiming at the problems of large dv/dt and di/dt in traditional single-ended converters and high electromagnetic interference (EMI) noise levels, a single-ended isolated converter using the secondary resonance technique is proposed in this paper. In the proposed converter, the voltage stress of the main power switch can be reduced and the voltage across the output diode is clamped to the output voltage when compared to the conventional flyback converter. In addition, the peak current stress through the main power switch can be decreased and zero current switching (ZCS) of the output diode can be achieved through the resonance technique. Moreover, the EMI noise coupling path and an equivalent model of the proposed converter topology are presented through the operational principle of the proposed converter. Analysis results indicate that the common mode (CM) EMI noise and the differential mode (DM) EMI noise of such a converter are deduced since the frequency spectra of the equivalent controlled voltage sources and controlled current source are decreased when compared with the traditional flyback converter. Furthermore, appropriate parameter selection of the resonant circuit network can increase the equivalent impedance in the EMI coupling path in the low frequency range, which further reduces the common mode interference. Finally, a simulation model and a 60W experimental prototype of the proposed converter are built and tested. Experimental results verify the theoretical analysis.

• Journal of the Optical Society of Korea
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• v.7 no.4
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• pp.253-257
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• 2003

We propose and demonstrate a novel polarization- and wavelength-independent digital electrooptic switch in $Ti:LiNbO_3$ with switching voltage of ${\pm}$32V at $1.55{\mu}m$ wavelength. This $2{\times}2$ integrated optic switch is characterized by a step-like response to the applied voltage. Switching is achieved through adiabatic mode evolution in an asymmetric waveguide junction. An average insertion loss of ∼4.5dB and polarization independent switching with average crosstalk of -12dB are achieved.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1110-1113
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• 2002

A Single-Stage Single-Switch power-factor- correction(PFC) AC/DC Converter with universal input is presented in this paper. The PFC Converter can be achieved based upon the continuous current mode(CCM). The switch has less current and voltage stresses over a wide range of load variation so that a low voltage rating device can be used. The presented converter features high power factor high efficiency, and low cost. An 90W prototype was implemented to show that it has 70% efficiency with low voltage stress over universal line input.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.92-96
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• 2003

This paper deals with the characteristics of persistent current switch (rCS) system fer applied HTS magnet system. To apply the high-Tc superconductor in superconducting machine such as motror, generator, MAGLEV, MRI, and NMR, the study on high-Tc superconducting persistent current mode must be performed. In this experiment, the PCS system consists otd superconducting magnet, PCS and magnet power supply. The superconducting magnet was fabricated by connecting four double pancake coils (DPCs) in series. The PCS was inductive double pancake coil type and heated up by the SUS 303L tape heater. The optimal length of PCS was calculated and thermal quench state of PCS was simulated by using finite element method(FEM) and compared with experimental results. The optimal energy to normalize the PCS was calculated and introduced. Finally, the persistent current was observed with respect to various ramping up rate and magnitude of charging current.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.528-531
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• 1994

In this paper, the resonant switch model applicable to the DC and small signal analysis of the resonant converter is studied because the conventional PWM switch model can't be applied to the analysis of the resonant converter. The charge control is superior to the peak current control in QRC because QRC is operated in FM mode. So the charge control technique is adopted and used to compose the ZVS-QRC boost with feedback loop.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.406-408
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• 2005

In this literature, when the utility line is normal, the Off-Line UPS operates as an active power filter to compensate the reactive power from a load, and when the utility line is in outage, the On-Line UPS opuates as in single phase inverter to supply an active and reactive power to the load. An additional static switch in UPS was used to decrease an transient state during these mode changes. And the result shows that the transient state disappeared.

• Journal of Power Electronics
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• v.9 no.6
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• pp.929-939
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• 2009

This paper presents a new soft-switching boost converter based on the LC resonance and passive clamping technique without additional active switches. The circuit achieves high efficiency and low voltage stress by adopting a soft switching method using LC resonance. This paper gives a mathematical analysis of each mode and a detailed design procedure of the proposed boost converter. First of all, the operational principles are verified through simulation results. Then, according to the design procedure, we designed and built a 1.5[kW] prototype soft switching boost converter. Through the experimental results, we demonstrated the validity and usefulness of the proposed boost converter.